Back to the Future Part II is a 1989 American science fiction comedy film and the second installment of the Back to the Future trilogy. As with all three films, it was directed by Robert Zemeckis, scripted by Bob Gale, and stars Michael J. Fox, Christopher Lloyd, Thomas F. Wilson and Lea Thompson. The plot of Part II picks up where the original film left off. After repairing the damage to history done by his previous time travel adventures, Marty McFly (Fox) and his friend Dr. Emmett "Doc" Brown (Lloyd) travel to 2015 to prevent McFly's future son from ending up in jail. However, their presence there allows Biff Tannen (Wilson) to steal Doc's DeLorean time machine and travel to 1955, where he alters history by making his younger self wealthy.

Part II was produced on a $40 million budget and was filmed back-to-back with its sequel, Back to the Future Part III. Filming began in February 1989 after two years was spent building the sets and writing the script. The film was one of the most ground-breaking projects for effects studio Industrial Light & Magic; in addition to digital compositing, ILM used the VistaGlide motion control camera system, which allowed scenes to be filmed in which an actor played multiple characters on-screen. Two actors from the first film, Crispin Glover and Claudia Wells, did not return for the final two films; Glover's character, George McFly, was not only minimized in the plot but was also obscured otherwise and was recreated with another actor. Part II was released by Universal Pictures on November 22, 1989. The film received generally favorable reviews, although not as strong as the first installment. A commercial success, Part II grossed $331,950,002 worldwide, making it the third-highest-grossing film of the year.

Plot

On October 26, 1985, Dr. Emmett Brown arrives in his DeLorean time machine and persuades Marty McFly and his girlfriend, Jennifer Parker to come with to the future to prevent their future children from being imprisoned. As they depart, Biff Tannen witnesses their departure. They arrive on October 21, 2015, where Doc electronically hypnotizes Jennifer and leaves her incapacitated in an alley. Meanwhile, Doc has Marty pose as Marty McFly, Jr., Marty's future son, to refuse an offer to participate in a robbery with Biff's grandson, Griff.

Marty successfully switches places with his son and refuses Griff's offer. However, Griff goads Marty into a fight, during which Griff and his gang crash into the local courthouse and are arrested, saving Marty's future children. Before regrouping with Doc, Marty purchases Grays Sports Almanac, a book detailing the results of major sporting events from 1950–2000. Doc discovers the purchase and warns him about attempting to profit from time travel, but before Doc can adequately dispose of the almanac, they are forced to follow police who have found Jennifer incapacitated and are taking her to her 2015 home. 2015 Biff, overhearing the conversation and recalling the DeLorean from 1985, follows in a taxi with the discarded book.

Jennifer wakes up in her 2015 home and hides from the McFly family. She overhears that her future self's life with Marty is not what they expected due to a car accident involving Marty. She witnesses the 2015 Marty being goaded into a shady business deal by his co-worker Needles, causing their supervisor to dismiss Marty, as announced by numerous faxes (one of which Jennifer keeps). While escaping the house, Jennifer encounters her 2015 self and they both faint. While Marty and Doc attend to 1985 Jennifer, Biff uses the DeLorean to travel to 1955, where he gives his teenage self the almanac, before returning to 2015. Marty, Doc, and an unconscious Jennifer return to 1985, unaware of Biff's actions.

Marty and Doc soon discover that the 1985 to which they returned has changed dramatically: Biff has become wealthy and corrupt, and has changed Hill Valley into a chaotic dystopia; Marty's father, George, was killed in 1973, and Biff has forced his mother, Lorraine, to marry him instead; Doc has been committed to an insane asylum, while Marty, Dave and Linda are away at boarding schools. Doc finds evidence of the sports almanac and Biff's trip to 1955 in the DeLorean and asks Marty to find out when the 1955 Biff received the almanac so they can correct the timeline. Marty confronts Biff, who explains that he received the book on November 12, 1955 from an old man who instructed him to bet on every winner in the almanac. He was also told to eliminate anyone who questioned him about the almanac, and as a result, Biff attempts to kill Marty. During their encounter on his hotel roof, Biff reveals that he shot George. However, Doc arrives and incapacitates Biff, allowing him and Marty to flee to 1955.

Marty secretly follows the 1955 Biff and witnesses him receive the almanac from his older self, but Marty is initially unable to retrieve the book. Marty follows Biff to the high school's Enchantment Under the Sea Dance, being careful to avoid interrupting the events from his previous visit to the dance. Eventually, Biff leaves the dance with the almanac as Doc and Marty pursue. After a struggle, Marty takes the almanac from Biff, who crashes his car into a manure truck as Doc and Marty fly away in the DeLorean.

With Doc hovering above in the DeLorean as a storm approaches, Marty burns the almanac on the ground and undoes the damage to history that Biff has done. However, the time machine is struck by lightning and disappears. A courier from Western Union arrives minutes later and hands Marty a 70-year-old letter. It is from Doc, who was sent back in time to 1885 after the lightning strike and is now trapped. Marty races back into town and finds the 1955 Doc, who seconds earlier just helped the original Marty from the first film return to 1985. Doc is shocked by his friend's sudden reappearance and faints.